/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.runtime.state.heap;

import org.apache.flink.annotation.Internal;
import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.runtime.state.RegisteredKeyValueStateBackendMetaInfo;
import org.apache.flink.runtime.state.StateSnapshotTransformer;

import javax.annotation.Nonnull;

/**
 * This implementation of {@link StateTable} uses {@link NestedStateMap}.
 *
 * @param <K> type of key.
 * @param <N> type of namespace.
 * @param <S> type of state.
 */
@Internal
public class NestedMapsStateTable<K, N, S> extends StateTable<K, N, S> {

    /**
     * Creates a new {@link NestedMapsStateTable} for the given key context and meta info.
     *
     * @param keyContext the key context.
     * @param metaInfo the meta information for this state table.
     * @param keySerializer the serializer of the key.
     */
    public NestedMapsStateTable(
            InternalKeyContext<K> keyContext,
            RegisteredKeyValueStateBackendMetaInfo<N, S> metaInfo,
            TypeSerializer<K> keySerializer) {
        super(keyContext, metaInfo, keySerializer);
    }

    @Override
    protected NestedStateMap<K, N, S> createStateMap() {
        return new NestedStateMap<>();
    }

    // Snapshotting
    // ----------------------------------------------------------------------------------------------------

    @Nonnull
    @Override
    public NestedMapsStateTableSnapshot<K, N, S> stateSnapshot() {
        return new NestedMapsStateTableSnapshot<>(
                this,
                getKeySerializer(),
                getNamespaceSerializer(),
                getStateSerializer(),
                getMetaInfo()
                        .getStateSnapshotTransformFactory()
                        .createForDeserializedState()
                        .orElse(null));
    }

    /**
     * This class encapsulates the snapshot logic.
     *
     * @param <K> type of key.
     * @param <N> type of namespace.
     * @param <S> type of state.
     */
    static class NestedMapsStateTableSnapshot<K, N, S> extends AbstractStateTableSnapshot<K, N, S> {

        NestedMapsStateTableSnapshot(
                NestedMapsStateTable<K, N, S> owningTable,
                TypeSerializer<K> localKeySerializer,
                TypeSerializer<N> localNamespaceSerializer,
                TypeSerializer<S> localStateSerializer,
                StateSnapshotTransformer<S> stateSnapshotTransformer) {
            super(
                    owningTable,
                    localKeySerializer,
                    localNamespaceSerializer,
                    localStateSerializer,
                    stateSnapshotTransformer);
        }

        @Override
        protected StateMapSnapshot<K, N, S, ? extends StateMap<K, N, S>>
                getStateMapSnapshotForKeyGroup(int keyGroup) {
            NestedStateMap<K, N, S> stateMap =
                    (NestedStateMap<K, N, S>) owningStateTable.getMapForKeyGroup(keyGroup);

            return stateMap.stateSnapshot();
        }

        @Override
        public void release() {}
    }
}
